Lactones are known to possess useful organoleptic properties and have been employed as flavor and fragrance materials. For example, Maga, in a comprehensive survey published in "Critical Reviews in Food Science and Nutrition", September, 1976, pp 1-56, summarized the aroma and flavor properties of naturally derived lactones. According to Maga, gamma-hexalactone possesses a herbaceous, sweet odor with a coumarin, caramel taste. Gamma-octalactone has a fruity, coconut odor and taste, while gamma- and delta- decalactones exhibit a fruity, peach-like odor and taste.
The herbaceous or fruit origin of many of the foregoing lactones has been well established. However, their isolation from plant material by extraction or distillation is often impractical or impossible because they are present in extremely low concentrations. Consequently, synthetic reaction methods are often used to manufacture lactones for use as flavor and fragrance materials.
Lactones have also been identified among the metabolites of various microorganisms. For example, Collins and Halim (J. Agric. Food Chem., 1972, 20, 437) identified the delta-lactone, 6-pentyl-2-pyrone, as the predominant volatile material arising from a culture containing the soil fungus Trichoderma viride. Drawert, et. al. (Chem. Mikrobiol. Technol. Lebensum., 1983, 8, 91) identified milligram quantities of C.sub.3 -C.sub.8 gamma-lactones from cultures of Polyporus durus in a nutrient broth. Likewise, similar yields of a series of gamma-lactones from a cultured malt broth of Fusarium poae were reported by Sarris and Latrasse (Agric. Biol. Chem., 1983, 49, 3227). U.S. Pat. No. 4,542,097 discloses the use of Pityrosporum cultures for the production of mixtures of gamma-lactones in low yields. Tahara, et. al., (Agric. Biol. Chem., 1972, 36, 2585) found that the microorganism Sporobolomyces odorus produced milligram quantities of gamma-decalactone in a 15 L fermentation broth after an extended incubation period.
The metabolism of ricinoleic acid by several Candida strains was investigated by Okui, et. al., (J. Biochemistry, 1963, 54, 536) who showed that gamma-hydroxydecanoic acid was an intermediate in the oxidative degradation pathway. Farbood and Willis in U.S. Pat. No. 4,560,656, studied this beta-oxidation process in greater detail with castor oil. With a variety of microorganisms, they were able to produce gamma-hydroxydecanoic acid and subsequently gammadecalactone at a level of 5 to 6 grams per liter of fermentation broth.
Methods have also been disclosed for the preparation of certain optically active lactones and the corresponding hydroxy carboxylic acids through microbial reduction of ketocarboxylic acids. For example, U.S. Pat. No. 3,076,750 discloses a process for the microbial reduction of 4- and 5-ketocarboxylic acids having from 5 to 18 carbon atoms.
The use of a microbial process to produce lactones, such as those described above, would appear to have advantages over synthetic methods because the microbial process combines into a single step the multiple reactions required by a synthetic method. Moreover, the microbial process would satisfy the desire to obtain flavor and fragrance material from natural sources.
However, like processes utilizing plant extraction, the microbial processes described in the literature suffer from extremely poor yields and are not general in nature. They produce only certain, specific lactones and are not known to be useful for the production of lactones of varying molecular weight.
Accordingly, it is an object of the invention to develop a microbiological process for the production of lactones of variable carbon chain length. It is also desired to produce gamma or delta lactones. Yet another object is the microbiological production of such lactones with yields that will establish economical lactone manufacture. A further object is the production of lactones from the corresponding saturated or unsaturated carboxylic acids or derivatives thereof.